Ships and other marine vessels include hatches formed in horizontal surfaces and doors formed in vertical surfaces to allow crewmembers and goods to pass through. A hatch or door must be watertight around all of its edges and sufficiently stiff and strong to withstand the forces applied during use. Hatches are typically formed of metal and are heavy to open and close. Thus, a scuttle sized to allow passage of a singe person is typically provided within the hatch. The scuttle must also be watertight. The operating mechanisms to open and close both the hatch and the scuttle are conventionally provided on the hatch itself, adding to the weight.
Hatches and scuttles on ships are traditionally made from steel. During many years of marine service, steel hardware has proven to be relatively inexpensive, to have good resistance to damage from routine operational impacts, to provide inherent EMI and EMP shielding, and to perform well in standard fire tests.
Steel hatches and scuttles have several drawbacks, however. Life cycle costs can be high, due to considerable routine maintenance, such as regular painting to prevent corrosion. Also, the heavy weight makes opening and closing of the hatch and/or scuttle unsafe, particularly in rough weather or in other difficult or dangerous circumstances.